"We are all in a journey to become complete human beings," the 75-year-old Farrakhan told the crowd of thousands gathered inside Mosque Maryam and in white tents outside. "Look how we have become so divided, so hateful, while claiming the same creator."
Farrakhan renewed a call for many to get back to the basic tenets of Islam, while still encouraging black pride.
"Black people must stop seeing themselves as inferior, and whites must stop seeing themselves as superior," he said, adding that black Muslims "have to keep going our own way."
Though other religious leaders and non-Muslims were invited to the public event, most of those in attendance were Nation of Islam followers.
Farrakhan did not lay out any specific plans for the "new beginning," but he offered his opinion on many topics and made a plea for understanding with immigrants south of U.S. borders.
"Our brothers and sisters from South America are not trying to take your jobs. They are trying to survive," Farrakhan said.
Noting the current economic turmoil, he said, "God is troubling America because America can do better." He noted the theme of "change" in the presidential election and said change must also come through religious communities.
"The change that will feed our hearts is not necessarily a political change," he said. "Our mission is to help bring in a government of peace."
In February, Farrakhan appeared at an annual Saviours' Day event in Chicago and called Democratic presidential candidate Barack Obama the "hope of the entire world" that the U.S. will change for the better.
The Obama campaign quickly denounced Farrakhan's support because he has made comments in the past widely viewed as being anti-Semitic. Nation of Islam officials said Farrakhan's statements are often taken out of context.
Farrakhan ceded leadership of the Nation in 2006 as he recuperated from complications of prostate cancer, but not long afterward quietly retook full responsibility for the organization.
The Chicago event comes just weeks after the death of Imam W.D. Mohammed, the son of Nation founder Elijah Muhammad, who broke with the group and moved thousands of African-Americans toward mainstream Islam.
While the Nation has espoused black nationalism and self-reliance since it was founded in the 1930s, in recent years members have reached out to other groups. For instance, the Nation has a Latino liaison and has become involved in immigrant rights rallies and marches.
Farrakhan has haltingly tried to move the Nation toward traditional Islam, which considers the American movement heretical because of its view of Elijah Muhammad as a prophet, among other novel teachings. Orthodox Islam teaches that there has been no prophet after Prophet Muhammad in the seventh century.
He has also downplayed some of the group's more controversial beliefs. The Nation of Islam has taught that whites are descended from the devil and that blacks are the chosen people of Allah.
Sunday's event was a rededication to the historic 1948 building. The mosque, once a Greek Orthodox church, has undergone major renovations, including getting new marble floors, since it was bought by the Nation in 1972.
It also wrapped up a week of commemoration of the 13th anniversary of the Million Man March, a political gathering in Washington that encouraged the empowerment of blacks and that Farrakhan spearheaded in 1995.